Elements in the Sun. 



821 



The following is an experimental work by Loving on the 

 comparative intensities of Ca and Mg lines in ordinary arc 

 and vacuum arc. (Astrophysical Journal, vol. xxii. p. 300, 

 1905.) Fowler also noted that the enhanced lines of Mg, Zn, 

 and Cd are greatly intensified in a vacuum arc (Fowler and 

 Payn, Proc. Roy. Soc. lxxii. 1903). 



Element. 



Open 

 arc. 



Vacuum 

 arc. 



Relative 



weakening. 



Spark. 



Chromo- 

 sphere. 



K-3934 



500 



25 



1 

 20 



1000 



75 



H-3W68 



300 



20 



15 



500 



60 



g-4227 



1000 



8 



1 

 125 



100 



8 



Magnesium. 



2852 



500 



8 



1 

 60 



100 





4481 (+Mg) 







20 



— 



50 



1 



Thus the tables show that in the vacuum arc the ratio 

 Ca + /Ca is 6-8 times its value in the ordinary arc. Unfor- 

 tunately the pressure, which is a vital point, is not stated. 

 In the case of Mg, the stimulus at the open arc is not even 

 sufficient to excite the ionized line 4481. But a diminution 

 in concentration brings about ionization. This case is rather 

 remarkable because it affords an experimental basis for the 

 view that temperature remaining the same, a diminished 

 concentration can bring about a higher stimulus. 



Conclusion. 



The foregoing work will probably make it clear that the 

 theory of temperature ionization developed by the author in 

 paper A, and more fully applied in the present paper, is 

 capable of throwing much light on many obscure and 

 puzzling questions of solar physics. We are precluded 

 from making further applications owing to lack of necessary 

 data, viz., the value of the ionization potential of elements 

 or the value of the term or terms (1, s). If this and the 

 spectral properties of all elements were known with as much 

 certainty and exactness as in the case of the alkaline earths, 

 details of the Fraunhol'er spectrum could be very satis- 

 factorily explained. 



We can, however, make the following suggestions with 



